Positively photosensitive resin composition

ABSTRACT

A positive-working radiation-sensitive resin composition showing a good throughput upon production of semiconductors or the like and less process dependence of dimensional accuracy as well as having high sensitivity and high resolution, and being able to form a pattern with good shape and a high aspect ratio. The positive-working radiation-sensitive resin composition comprises (i) a radiation-sensitive novolak resin comprising a reaction product between an alkali-soluble novolak resin from which low-molecular-weight components have been removed by fractional treatment and an o-naphthoquinonediazide compound, or a product obtained by removing low-molecular-weight components by fractional treatment from a reaction product between an alkali-soluble novolak resin and an o-naphthoquinonediazide compound, and (ii) a low-molecular compound represented by the general formula (I) and having phenolic hydroxyl group or groups:                    
     wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  each represents independently H, a C 1  to C 4  alkyl group, a C 1  to C 4  alkoxyl group, a cyclohexyl group or a group represented by the formula:                    
     wherein R 8  represents H, a C 1  to C 4  alkyl group, a C 1  to C 4  alkoxyl group or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b, c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5, c+d≦5, e+f≦5, and g+h≦5; and i is 0, 1 or 2.

TECHNICAL FIELD

This invention relates to a novel positive-working radiation-sensitiveresin composition and, more particularly, to a positive-workingradiation-sensitive resin composition containing a radiation-sensitivenovolak resin, suited for manufacture of semiconductors, production of adisplay surface of liquid crystal display panel, manufacture of acircuit substrate for thermal head etc., and like use.

BACKGROUND ART

In the wide field of manufacturing semiconductor integrated circuitssuch as LSI, preparing a display surface of liquid crystal displaypanel, manufacturing a circuit substrate for thermal head etc., and likeuse, photolithography has so far been employed for forming microelementsor conducting fine processing. In the photolithography, a positive- ornegative-working radiation-sensitive resin composition is used forforming a resist pattern. Of these radiation-sensitive resincompositions, those compositions containing an alkali-soluble resin anda photosensitizer of quinonediazide compound are most popularly used asthe positive-working radiation-sensitive resin compositions. As suchcompositions, there are described compositions having differentformulations as, for example, ‘novolak resin/quinonediazide compound’ inmany documents such as Japanese Examined Patent Publication No.S54-23570 (U.S. Pat. No. 3,666,473), Japanese Examined PatentPublication No.56-30850 (U.S. Pat. No. 4,115,128), Japanese UnexaminedPatent Publication Nos. S55-73045, S61-205933 and S62-51459, etc.

These compositions containing a novolak resin and a quinonediazidecompound have so far been studied with respect to both novolak resinsand photosensitizers. In respect of novolak resins, there have beendeveloped novel resins. In addition, radiation-sensitive resincompositions having excellent properties have also been obtained byimproving properties of conventionally known resins. For example, thereare disclosed techniques providing a radiation-sensitive resincomposition having excellent properties by using a novolak resin with aparticular molecular weight distribution in Japanese Unexamined PatentPublication Nos. S60-140235 and H1-105243 and by using a novolak resinfrom which low-molecular-weight components of the resin has been removedin Japanese Unexamined Patent Publication Nos. S60-97347, S60-189739 andJapanese Patent Publication No.2590342.

A number of positive-working radiation-sensitive resin compositionscontaining quinonediazide compounds have been put into practice as aresult of various technical developments having so far been made, andthe aspect ratio of thickness of radiation-sensitive resin coating toresolved line width has been improved to about 5:1.

On the other hand, degree of integration of integrated circuits ofsemiconductor elements have been increased year by year and, in themanufacture of semiconductor elements or the like, processing ofpatterns with a line width of less than sub-micron order has becomerequired. In the uses requiring such super-fine processing, good patternreproducibility is required as well as high resolution and, from thestandpoint of production cost, it is also required to improve throughput(yield per unit time) upon production. Therefore, increasing sensitivityof radiation-sensitive resin composition and reducing dependence ofdimensional accuracy upon process are also important factors. However,conventionally known radiation-sensitive resin compositions can notsatisfy these requirements at the same time, thus being insufficient.

An object of the present invention is to provide a radiation-sensitiveresin composition capable of satisfying all of these conventionallydesired properties at the same time, i.e., a radiation-sensitive resincomposition which has a high sensitivity and a high resolution, whichcan form a good pattern with a high aspect ratio, and which provides anexcellent throughput upon production and has a small dependence ofdimensional accuracy upon process.

DISCLOSURE OF THE INVENTION

As a result of intensive investigations, the inventors have found thatthe above-described object can be attained by using a positive-workingradiation-sensitive resin composition containing a specificradiation-sensitive novolak resin and a specific dissolution inhibitor,thus having achieved the present invention based on the finding.

That is, the present invention is a radiation-sensitive resincomposition which contains (i) a radiation-sensitive novolak resincomprising a reaction product between an alkali-soluble novolak resinfrom which low-molecular-weight components have been removed by afractional treatment and an o-naphthoquinonediazide compound, or aproduct obtained by removing low-molecular-weight components byfractional treatment from a reaction product between an alkali-solublenovolak resin and an o-naphthoquinonediazide compound and (ii) adissolution inhibitor comprising a low-molecular compound represented bythe following general formula (I) and having phenolic hydroxyl group orgroups:

wherein R₁, R₂, R₃, R₄, R₅, R₆ and R₇ each represents independently H, aC₁ to C₄ alkyl group, a C₁ to C₄ alkoxyl group, a cyclohexyl group or agroup represented by the formula:

wherein R₈ represents H, a C₁ to C₄ alkyl group, a C₁ to C₄ alkoxylgroup or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b,c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5,c+d≦5, e+f≦5, and g+h≦5; and i is 0, 1 or 2.

The present invention will now be described more specifically below.

An alkali-soluble novolak resin from which low-molecular-weightcomponents have been removed by fractional treatment to be used as astarting material for preparing the radiation-sensitive novolak resin ofthe present invention may be manufactured by removinglow-molecular-weight components by fractional treatment from thenovolak-type phenol resin obtained by polycondensation between at leastone of phenols and an aldehyde such as formalin.

As the phenols to be used for manufacturing this alkali-soluble novolakresin, there may be illustrated cresols such as o-cresol, p-cresol andm-cresol; xylenols such as 3,5-xylenol, 2,5-xylenol, 2,3-xylenol and3,4-xylenol; trimethylphenols such as 2,3,4-trimethylphenol,2,3,5-trimethylphenol, 2,4,5-trimethylphenol and 3,4,5-trimethylphenol;t-butylphenols such as 2-t-butylphenol, 3-t-butylphenol and4-t-butylphenol; methoxyphenols such as 2-methoxyphenol,3-methoxyphenol, 4-methoxyphenol, 2,3-dimethoxyphenol,2,5-dimethoxyphenol and 3,5-dimethoxyphenol; ethylphenols such as2-ethylphenol, 3-ethylphenol, 4-ethylphenol, 2,3-diethylphenol,3,5-diethylphenol, 2,3,5-triethylphenol and 3,4,5-triethylphenol;chlorophenols such as o-chlorophenol, m-chlorophenol, p-chlorophenol and2,3-dichlorophenol; resorcinols such as resorcinol, 2-methylresorcinol,4-methylresorcinol and 5-methylresorcinol; catechols such as5-methylcatechol; pyrogallols such as 5-methylpyrogallol; bisphenolssuch as bisphenol A, B, C, D, E or F; methylol-cresols such as2,6-dimethylol-p-cresol; naphthols such as α-naphthol, β-naphthol, etc.;and the like. These are used independently or as a mixture of two ormore thereof.

As the aldehydes, there may be used salicylaldehyde, paraformaldehyde,acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde,etc. independently or as a mixture of two or more thereof as well asformalin.

The polycondensation between at least one of phenols and an aldehydesuch as formalin may be conducted by any conventionally known orwell-known processes such as using, for example, oxalic acid as acatalyst. As a method of fractional treatment for removinglow-molecular-weight components from the novolak resin obtained, anyconventionally known processes may be adapted. The method of fractionaltreatment include e.g. liquid-liquid fractionation of novolak resinusing two different solvents having different dissolution abilities tothe component of the resin, a method of removing low-molecular-weightcomponents by centrifugation, etc.

Removal of the low-molecular-weight components from the novolak resinmay be conducted after reaction between the novolak resin and theo-naphthoquinonediazide compound. However, the removal is preferablyconducted before reaction of the two since there is no fear of thephotosensitizer being deactivated by the heat applied upon fractionaltreatment and from the standpoint of the safety. Additionally, thefractional treatment of the reaction product can be conducted in thesame manner as with fractional treatment of novolak resins.

The alkali-soluble novolak resin to be used in the present inventionfrom which low-molecular-weight components have been removed must show adissolution rate of 10-180 Å/sec, preferably 20-150 Å/sec, for a 2.38 wt% aqueous solution of tetramethylammonium hydroxide measured accordingto the following “method for measuring dissolution rate of novolakresin”. If the dissolution rate is less than 10 Å/sec, such novolakresin can cause reduction in sensitivity and remaining of undissolvedmatter, and fails to provide enough resolution, whereas if more than 180Å/sec, there results such a decrease in film thickness after developmentthat good patterns are hardly obtained.

(Method for Measuring Dissolution Rate of Novolak Resin)

20 g of novolak resin is dissolved in 80 g of a mixed solvent of ethyllactate/n-butyl acetate (85/15), then filtered through a 0.5 μm Teflonfilter. The resulting resin solution is coated on a HMDS-treated 4-inchsilicon wafer using a spin coater, LARC ULTIMA-1000 made by LithotecJapan Co. in a thickness of about 1 μm after being baked at 100° C. for90 seconds on a hot plate. After baking at 100° C. for 90 seconds on ahot plate, thickness of the coating is accurately measured by means ofan apparatus for measuring film thickness, Lambda Ace made by DainipponScreen Co., Ltd. Thereafter, the thus obtained silicon wafer is dippedin an alkaline developer solution, AZ® 300MIF Developer (a 2.38 wt %aqueous solution of tetramethylammonium hydroxide) made by Clariant(Japan) K. K. at 23° C., and the time necessary for the resin coating onthe wafer to be completely dissolved is measured. Dissolution rate ofnovolak resin is calculated from the coating thickness and thedissolution time thus measured.

On the other hand, o-naphthoquinonediazide compounds to be used asstarting material for manufacturing the radiation- sensitive novolakresin of the present invention may be any of those which haveconventionally been known as a photosensitizer for radiation-sensitiveresin compositions or have conventionally been used in manufacturing aphotosensitizer and which keep their radiation sensitivity even afterreaction with novolak resin. As the o-naphtoquinonediazide compoundthere may be illustrated, for example, 1,2-naphthoquinonediazidesulfonic acid halides such as 1,2-naphthoquinonediazide-4-sulfonic acidchloride, 1,2-naphthoquinonediazide-5-sulfonic acid chloride,1,2-naphthoquinonediazide-6-sulfonic acid chloride and the like. Theseo-naphtoquinonediazide compounds may be used independently or as amixture of two or more thereof. The radiation-sensitive novolak resin ofthe present invention may be a single radiation-sensitive novolak resinor a mixture of two or more of radiation-sensitive novolak resins. Inthe case of using a mixture of two or more radiation-sensitive novolakresins as the radiation-sensitive novolak resin, suchradiation-sensitive novolak resins may be prepared by respectivelyreacting novolak resins with a single different o-naphthoquinonediazidecompound, followed by mixing these two or more radiation-sensitivenovolak resins or, alternatively, by reacting previously mixedo-naphthoquinonediazide compounds with novolak resin, with the formermanner of independently reacting o-naphthoquinonediazide compound withnovolak resin being preferred. The preferable examples ofo-naphthoquinonediazide compound in the present invention are1,2-naphthoquinonediazide-5-sulfonic acid chloride alone and thecombination of 1,2-naphthoquinonediazide-4-sulfonic acid chloride and1,2-naphthoquinonediazide-5-sulfonic acid chloride.

The reaction between the alkali-soluble novolak resin and theo-naphthoquinonediazide compound may be carried out in any ofconventionally known manners, for example, by dissolving both thealkali-soluble novolak resin and the o-naphthoquinonediazide sulfonicacid chloride in a solvent, and dropwise adding an organic aminesolution to this solution. As to reaction substitution ratio of theo-naphthoquinonediazide compound to the alkali-soluble novolak resinfrom which low-molecular-weight components have been removed, 3-25 mol %based on hydrogen atom of hydroxyl group of said novolak resin ispreferred, with 4-15 mol % being more preferred. If the reactionsubstitution ratio is less than 3 mol %, intended resolution is hardlyattained, whereas if more than 25 mol %, there tends to result apositive pattern with undeveloped residues.

As the low-molecular compound to be used as a dissolution inhibitor inthe radiation-sensitive resin composition of the present invention,which is represented by the above general formula (I) and has a phenolichydroxyl group or groups, there are illustrated, for example,4,4′,4″-methylidinetrisphenol,2,6-bis[(2-hydroxy-5-methylphenol)methyl]-4-methylphenol,4,4′-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol,4,4′,4″-ethylidinetrisphenol,4-[bis(4-hydroxyphenyl)methyl]-2-ethoxyphenol,4,4′-[(2-hydroxyphenyl)methylene]bis[2,3-dimethylphenol],4,4′-[(3-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],4,4′-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],2,2′-[(2-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],2,2′-[(4-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],4,4′-[(3,4-dihydroxyphenyl)methylene]bis [2,3,6-trimethylphenol],4-[bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)methyl]-1,2-benzenediol,4,6-bis[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,2,3-benzenetriol,4,4′-[(2-hydroxyphenyl)methylene]bis[3-methylphenol],4,4′,4″-(3-methyl-1-propanyl-3-ylidine)trisphenol,4,4′,4″,4′″-(1,4-phenylenedimethylidine)tetrakisphenol, 2,4,6-tris[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,3-benzenediol,2,4,6-tris[(3,5-dimethyl-2-hydroxyphenyl)methyl]-1,3-benzenediol,4,4′-[1-[4-[1-[4-hydroxy-3,5-bis[(hydroxy-3-methylphenyl)methyl]phenyl]-1-methylethyl]phenyl]ethylidene]bis[2,6-bis(hydroxy-3-methylphenyl)methyl]phenol,and the like. These low-molecular compounds having phenolic hydroxylgroup or groups are used in an amount of usually 2 to 20 parts byweight, preferably 5 to 15 parts by weight, per 100 parts by weight ofthe radiation-sensitive novolak resin.

The radiation-sensitive novolak resin and the dissolution inhibitor oflow-molecular compound having a phenolic hydroxyl group or groups of thepresent invention are dissolved in a solvent to form a positive-workingradiation-sensitive resin composition. The solvent for dissolving thesecomponents includes ethylene glycol monoalkyl ethers such as ethyleneglycol monomethyl ether and ethylene glycol monoethyl ether; ethyleneglycol monoalkyl ether acetates such as ethylene glycol monomethyl etheracetate and ethylene glycol monoethyl ether acetate; propylene glycolmonoalkyl ethers such as propylene glycol monomethyl ether and propyleneglycol monoethyl ether; propylene glycol monoalkyl ether acetates suchas propylene glycol monomethyl ether acetate and propylene glycolmonoethyl ether acetate; lactates such as methyl lactate and ethyllactate; aromatic hydrocarbons such as toluene and xylene; ketones suchas methyl ethyl ketone, 2-heptanone and cyclohexanone; amides such asN,N-dimethylacetamide and N-methylpyrrolidone; and lactones such asγ-butyrolactone. These solvents can be used independently or as amixture of two or more thereof.

A photosensitizer containing a quinonediazide group may be incorporatedinto the positive-working radiation-sensitive resin composition of thepresent invention as necessary. The photosensitizer is obtained byallowing naphthoquinonediazidesulfonic acid chloride orbenzoquinonediazidesulfonic acid chloride to react with a low-molecularor high-molecular compound having a functional group capable ofcondensation reaction with these acid chlorides. The functional groupthat can be condensed with an acid chloride includes a hydroxyl group,an amino group etc. Among these, a hydroxyl group is particularlypreferable. The compound containing a hydroxyl group includes e.g.hydroquinone; resorcinol; hydroxybenzophenones such as2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone,2,4,6-trihydroxybenzophenone, 2,4,4′-trihydroxybenzophenone,2,3,4,4-tetrahydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone and2,2′,3,4,6′-pentahydroxybenzophenone; hydroxyphenylalkanes such asbis(2,4-dihydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane andbis(2,4-dihydroxyphenyl)propane; and hydroxytriphenylmethanes such as4,4′,3″,4″-tetrahydroxy-3,5,3′,5′-tetramethyltriphenylmethane and4,4′,2″,3″,4″-pentahydroxy-3,5,3′,5′-tetramethyltriphenylmethane. Thesecan be used independently or as a combination of two or more thereof.

Dyestuffs, adhesive aids, surfactants etc. conventionally used asadditives of the radiation-sensitive resin composition may beincorporated as necessary into the radiation-sensitive resin compositionof the present invention. The dyestuffs include e.g. Methyl Violet,Crystal Violet, Malachite Green etc.; the adhesive aids include e.g.alkyl imidazoline, butyric acid, alkyl acid, polyhydroxystyrene,polyvinylmethyl ether, t-butyl novolak, epoxy silane, epoxy polymer,silane etc.; and the surfactants include e.g. nonionic surfactants suchas polyglycols and derivatives thereof, that is, polypropylene glycol orpolyoxyethylene lauryl ether, fluorine-containing surfactants such asFluorad (trade name; manufactured by Sumitomo 3M Ltd.), Megafac (tradename; manufactured by Dainippon Ink & Chemicals, Inc.), Sulflon (tradename; manufactured by Asahi Glass Co., Ltd.) or organosiloxane surfaceactive agents such as KP341 (trade name; Shin-Etsu Chemical Co., Ltd.).

Furthermore, the radiation-sensitive resin composition of the presentinvention may be used in combination with an inorganic anti-reflectivecoating of TiN, SiN, SiON or the like or an organic anti-reflectivecoating of AZ® BARLi, AZ® BARLi II (manufactured by Clariant (Japan) K.K.).

The positive-working radiation-sensitive resin composition of thepresent invention is applied on a substrate such as a silicon waferhaving an anti-reflective coating thereon, by spin coating or the like,and the substrate on which the radiation-sensitive resin composition hasbeen coated is subjected to baking to form a radiation-sensitive resincoating. The substrate having thereon the radiation-sensitive resincoating is exposed with radiation such as ultraviolet rays, deepultraviolet rays, X-rays or electron beams and is developed with analkaline developing solution to form a resist pattern with highresolution and good pattern profile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a GPC chart of novolak resin A prepared in SynthesisExample 1.

FIG. 2 shows a GPC chart of novolak resin B prepared by subjectingnovolak resin A prepared in Synthesis Example 1 to fractional treatment.

BEST MODE FOR PRACTICING THE INVENTION

The present invention will now be described more specifically byreference to Examples which, however, are not to be construed to limitthe present invention in any way.

SYNTHESIS EXAMPLE 1

Synthesis and Fractional Treatment of Novolak Resin

80 g of m-cresol, 120 g of p-cresol, 112 g of a 37% formalin aqueoussolution and 0.32 g of oxalic acid were charged in a 1-liter separableflask equipped with a stirrer, a condenser and a thermometer, and heatedto 100° C. under stirring, followed by reacting for 16 hours.Thereafter, the temperature was raised to 200° C., and the pressure wasgradually reduced to 1 mmHg to thereby remove water, unreacted cresolmonomer, formaldehyde, oxalic acid, etc. Then, molten novolak resin wastaken out of the flask and cooled to room temperature to solidify andrecover the reaction product. Molecular weight of the thus obtainednovolak resin A was measured according to gel permeation chromatography(GPC). Results of the measurement are shown in FIG. 1. Weight averagemolecular weight of the novolak resin A as determined using polystyrenestandards was 6,800, dispersing degree (Mw/Mn) was 10.5, and contents ofdimer, trimer and tetramer were 12.1%, 4.2% and 4.5%, respectively.Dissolution rate of the novolak resin A for a 2.38 wt % aqueous solutionof tetramethylammonium hydroxide was 199 Å/sec.

Then, 100 g of this novolak resin A was completely dissolved in 234 g ofmethanol and 83.5 g of pure water was gradually added thereto understirring. After stirring for 10 minutes, 83.5 g of pure water wasfurther added gradually thereto under stirring. A precipitate formedduring stirring was filtered away. Further, this procedure cycle ofdissolution in methanol, washing with pure water and filtration wasrepeatedly conducted to obtain a white resin component. This resincomponent was heated to 40° C. and dried for 48 hours under reducedpressure to obtain novolak resin B. Molecular weight of the novolakresin B was measured according to GPC. Results of the measurement areshown in FIG. 2. The novolak resin B had a weight average molecularweight of 8,000 as determined using polystyrene standards, a dispersingdegree of 7.9, contents of dimer, trimer and tetramer of 7.1 %, 2.2 %and 3.3 %, respectively, and a dissolution rate of 40 Å/sec for a 2.38wt % aqueous solution of tetramethylammonium hydroxide.

Additionally, measurement according to GPC was conducted as follows.

GPC columns made by Showa Denko K. K. (one column of KF-804, two columnsof KF-802 and one column of KF-801) were used, and measurement wasconducted at a flow rate of 1.0 ml/min and at a column temperature of40° C. using tetrahydrofuran (THF) for liquid chromatography grade as amobile phase.

SYNTHESIS EXAMPLE 2

Synthesis of Radiation-sensitive Novolak Resin

60 g of the fractionation-treated novolak resin B prepared in SynthesisExample 1, 6.71 g of 1,2-naphthoquinonediazide-5-sulfonyl chloride and250 g of acetone were charged in a 1-liter, three-necked separable flaskequipped with a stirrer, a dropping funnel and a thermometer, andstirred to completely dissolve. Then, the flask was dipped in anice-bath till the temperature of the contents in the flask decreased to15° C. Then, 3.83 ml of triethylamine was dissolved in 25 ml of acetoneand charged in the dropping funnel, then dropwise added to the mixturein the flask over one hour. After stirring for further 10 minutes, thecontents inside the flask were filtered to remove triethylaminehydrochloride. Thereafter, the filtrate was gradually added dropwise to4, 000 ml of 0.1 N hydrochloric acid aqueous solution to obtain aprecipitate. This precipitate was washed with water, filtered out, anddried at 40° C. for 42 hours under reduced pressure to obtainradiation-sensitive novolak resin C.

EXAMPLE 1

45 g of radiation-sensitive novolak resin C, 5 g of a low-molecularcompound represented by the following formula (D-1) as a dissolutioninhibitor, and 0.05 g of a surfactant, Megafac R-08 (made by DainipponInk & Chemicals, Inc.) were dissolved in 80 g of a mixed solvent ofethyl lactate/n-butyl acetate (85/15). This solution was filteredthrough a 0.5 μm Teflon filter to obtain positive-workingradiation-sensitive resin composition 1.

The thus obtained positive-working radiation-sensitive resin composition1 was evaluated with respect to sensitivity, resolution, pattern form,scumming, and microgrooving properties according to the following“evaluation of radiation-sensitive resin composition”. Results thusobtained are tabulated in Table 1.

(Evaluation of Radiation-sensitive Resin Composition)

A radiation-sensitive resin composition is coated on a HMDS-treated4-inch silicon wafer using as a coater a spin coater, LARC ULTIMA-1000made by Lithotec Japan Co. in a thickness of about 6 μm after beingpre-baked at 110° C. for 120 seconds on a hot plate. After the coating,the radiation-sensitive resin coating was pre-baked at 110° C. for 120seconds on a hot plate, and thickness of the thus formedradiation-sensitive resin coating is measured by means of a filmthickness-measuring apparatus, Lambda Ace made by Dainippon Screen Co.,Ltd. This silicon wafer is exposed using a reduction projection alignerhaving an exposing wavelength of 365 nm (made by Hitachi Ltd.:LD-5015iCW, NA=0.50) with stepwise changing the exposure amount. Afterthe exposure, the wafer is developed by dipping in an alkaline developer(AZ® 300MIF developer, a 2.38 wt % aqueous solution oftetramethylammonium hydroxide) made by Clariant (Japan) K. K. at 23° C.for 5 minutes to obtain a positive resist pattern. Sensitivity,resolution, form of pattern, scumming and microgrooving properties areevaluated based on the thus obtained results according to the followingestimation standards.

(1) Sensitivity

Exposure energy capable of forming isolated 0.80 μm space as designed bya reticle pattern.

(2) Resolution

Minimum pattern dimension resolved by the above-described exposureamount.

(3) Form of Pattern

Cross-sectional form of the isolated space on the wafer on which aresist pattern has been formed is observed under a scanning electronmicroscope (SEM), and form of pattern is rated according to thefollowing criteria:

∘: No reduction in coating thickness observed, and increase of patterndimension at a height of 2/3 of the resist coating thickness from thesubstrate being less than +10% based on the bottom dimension of theisolated space;

Δ: No reduction in coating thickness observed, and increase of thepattern dimension being +10% to less than +15%;

X: Increase of the pattern dimension being +15% or more, or somereduction in coating thickness observed.

(4) Scumming

Form of isolated pattern at a critical resolution degree is observedunder a scanning electron microscope (SEM), and scumming is ratedaccording to the following criteria:

∘: No undeveloped residues observed on the substrate and at theinterface with resist pattern.

X: Undeveloped residues observed.

(5) Microgrooving

Isolated space pattern at the critical resolution degree is observedunder a scanning electron microscope (SEM), and presence ofmicrogrooving is rated according to the following criteria:

∘: No bites observed at the interface between resist pattern and thesubstrate.

X: Bites of pattern observed.

EXAMPLE 2

In the same manner as in Example 1 except for using as a dissolutioninhibitor a low-molecular compound represented by the following formula(D-2) in place of the low-molecular compound represented by the formula(D-1), there was obtained a positive-working radiation-sensitive resincomposition 2.

Sensitivity, resolution, form of pattern, scumming and microgroovingproperties of the positive-working radiation-sensitive resin composition2 were evaluated in the same manner as in Example 1. Results thusobtained are tabulated in Example 1.

Comparative Example 1

50 g of fractionation-treated radiation-sensitive novolak resin C and0.05 g of a surfactant of Megafac R-08 (product of Dainippon Ink &Chemicals, Inc.) were dissolved in 80 g of a mixed solvent of ethyllactate/butyl acetate (85/15). This solution was filtered through a 0.5μm Teflon filter to obtain a positive-working radiation-sensitive resincomposition 3. Sensitivity, resolution, form of pattern, scumming andmicrogrooving properties of the positive-working radiation-sensitiveresin composition 3 were evaluated in the same manner as in Example 1.Results thus obtained are tabulated in Table 1.

Comparative Example 2

Radiation-sensitive novolak resin E was obtained in the same manner aswith radiation-sensitive novolak resin C except for using novolak resinA not having been subjected to fractional treatment. 50 g of the thusobtained radiation-sensitive novolak resin E and 0.05 g of a surfactantof Megafac R-08 (product of Dainippon Ink & Chemicals, Inc.) weredissolved in 80 g of a mixed solvent of ethyl lactate/butyl acetate(85/15). This solution was filtered through a 0.5 pm Teflon filter toobtain a positive-working radiation-sensitive resin composition4.Sensitivity, resolution, form of pattern, scumming and microgroovingproperties of the positive-working radiation-sensitive resin composition4 were evaluated in the same manner as in Example 1. Results thusobtained are tabulated in Table 1.

Comparative Example 3

45 g of the radiation-sensitive novolak resin E, 5 g of a low-molecularcompound represented by the formula (D-1) as a dissolution inhibitor,and 0.05 g of a surfactant of Megafac R-08 (product of Dainippon Ink &Chemicals, Inc.) were dissolved in 80 g of a mixed solvent of ethyllactate/butyl acetate (85/15). This solution was filtered through a 0.5μm Teflon filter to obtain a positive-working radiation-sensitive resincomposition 5. Sensitivity, resolution, form of pattern, scumming andmicrogrooving properties of the positive-working radiation-sensitiveresin composition 5 were evaluated in the same manner as in Example 1.Results thus obtained are tabulated in Table 1.

TABLE 1 Radiation- Low-molecular sensitive phenol novolak resin compoundAdditive Additive Sensitivity Resolution Form of Name amount Name amount(mJ/cm²) (μm) pattern Scumming Microgrooving Example 1 C  90 D-1 10 6200.55 ◯ ◯ ◯ Example 2 C  90 D-2 10 585 0.55 ◯ ◯ ◯ Comparative C 100 — —920 0.80 × × × Example 1 Comparative E 100 — — 730 0.60 ◯ × × Example 2Comparative E  90 D-1 10 530 0.70 Δ × × Example 3

As is apparent from Table 1, the positive-working radiation-sensitiveresin compositions of the present invention show excellent sensitivityand resolution, form a pattern with good shape, form no scum, and showexcellent microgrooving properties.

Advantages of the Invention

As has been described in detail, the positive-workingradiation-sensitive resin composition of the present invention can showhigh sensitivity and high resolution and can form a pattern with goodshape and a high aspect ratio. In addition, it shows a good throughputupon production of semiconductors or the like and less processdependence of dimensional accuracy. Thus, it is extremely useful as aresist material for manufacturing semiconductor elements, production ofdisplay surface of LCD panel, production of circuit substrate of thermalheads, etc. wherein micro-patterning will become finer in the future.

Industrial Utility

The positive-working radiation-sensitive resin composition of thepresent invention can be preferably used as a resist material formanufacturing semiconductor elements, production of display surface ofLCD panel, production of circuit substrate of thermal heads and thelike.

What is claimed is:
 1. A positive-working radiation-sensitive resincomposition containing (i) a radiation-sensitive novolak resincomprising a reaction product between an alkali-soluble novolak resinfrom which low-molecular-weight components comprising dimers, trimersand tetramers have been removed by fractional treatment and ano-naphthoquinonediazide compound, or a product obtained by removinglow-molecular-weight components comprising dimers, trimers and tetramersby fractional treatment from a reaction product between analkali-soluble novolak resin and an o-naphthoquinonediazide compound,and (ii) a low-molecular compound represented by the general formula (I)and having phenolic hydroxyl group or groups:

wherein R₁, R₂, R₃, R₄, R₅, R₆ and R₇ each represents independently H, aC₁ to C₄ alkyl group, a C₁ to C₄ alkoxyl group, a Cyclohexyl group or agroup represented by the formula:

wherein R₈ represents H, a C₁ to C₄ alkyl group, a C₁ to C₄ alkoxylgroup or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b,c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5,c+d≦5, e+f≦5, and g+h≦5; and I is 0, 1 or 2; wherein said fractionaltreatment comprises removal of substantial amounts of said dimers,trimers and tetramers by precipitation.
 2. The positive-workingradiation-sensitive resin composition according to claim 1 wherein thedissolution rate of the alkali-soluble novolak resin from whichlow-molecular-weight components have been removed by fractionaltreatment, for a 2.38 wt % aqueous solution of tetramethylammoniumhydroxide, ranges from 10 to 180 Å/sec.
 3. The positive-workingradiation-sensitive resin composition according to claim 1 wherein thealkali-soluble novolak resin from which low-molecular-weight componentshave been removed by fractional treatment has a weight average molecularweight of 3,000 to 15,000 as determined using polystyrene standards, andthe reaction substitution ratio of the o-naphthoquinonediazide compoundbased on hydrogen atom of hydroxyl group in said alkali-soluble novolakresin is 3 to 25 mol %.
 4. The positive-working radiation-sensitiveresin composition according to claim 1 wherein the low-molecularcompound containing phenolic hydroxyl group or groups represented by thegeneral formula (I) is contained in an amount of 0.5 to 20 parts byweight relative to 100 parts by weight of the alkali-soluble novolakresin from which low-molecular-weight components have been removed byfractional treatment.